minetest/client/shaders/minimap_shader/opengl_fragment.glsl

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uniform sampler2D baseTexture;
uniform sampler2D normalTexture;
uniform vec3 yawVec;
varying lowp vec4 varColor;
varying mediump vec2 varTexCoord;
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void main (void)
{
vec2 uv = varTexCoord.st;
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//texture sampling rate
const float step = 1.0 / 256.0;
float tl = texture2D(normalTexture, vec2(uv.x - step, uv.y + step)).r;
float t = texture2D(normalTexture, vec2(uv.x - step, uv.y - step)).r;
float tr = texture2D(normalTexture, vec2(uv.x + step, uv.y + step)).r;
float r = texture2D(normalTexture, vec2(uv.x + step, uv.y)).r;
float br = texture2D(normalTexture, vec2(uv.x + step, uv.y - step)).r;
float b = texture2D(normalTexture, vec2(uv.x, uv.y - step)).r;
float bl = texture2D(normalTexture, vec2(uv.x - step, uv.y - step)).r;
float l = texture2D(normalTexture, vec2(uv.x - step, uv.y)).r;
float dX = (tr + 2.0 * r + br) - (tl + 2.0 * l + bl);
float dY = (bl + 2.0 * b + br) - (tl + 2.0 * t + tr);
vec4 bump = vec4 (normalize(vec3 (dX, dY, 0.1)),1.0);
float height = 2.0 * texture2D(normalTexture, vec2(uv.x, uv.y)).r - 1.0;
vec4 base = texture2D(baseTexture, uv).rgba;
vec3 L = normalize(vec3(0.0, 0.75, 1.0));
float specular = pow(clamp(dot(reflect(L, bump.xyz), yawVec), 0.0, 1.0), 1.0);
float diffuse = dot(yawVec, bump.xyz);
vec3 color = (1.1 * diffuse + 0.05 * height + 0.5 * specular) * base.rgb;
vec4 col = vec4(color.rgb, base.a);
col *= varColor;
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gl_FragColor = vec4(col.rgb, base.a);
}